该示例展示了如何创建一个带下拉菜单变量选择器的Altair热度图。

首先，我们来看一下原始代码：

import altair as alt
from vega_datasets import data

source = data.crime_heatmap.url

# Define the string of possible values
fields = ['total', 'property', 'violent', 'vehicle', 'burglary']

# Define the chart
heatmap = alt.Chart(source).mark_rect().encode(
    alt.X('year(date):O', title=None),
    alt.Y('month(date):O', title=None),
    alt.Color('sum(crimes):Q', scale=alt.Scale(scheme='yellowgreenblue')),
).properties(
    width=600,
    height=300,
    title='Monthly Crime Heatmap'
)

# Define the dropdown selector
field_dropdown = alt.binding_select(options=fields)
field_select = alt.selection_single(fields='total', bind=field_dropdown, name='Crime Type')

# Define the updated chart
heatmap_select = heatmap.transform_filter(
    field_select
).properties(
    title='Monthly Crime Heatmap by Crime Type'
)

# Combine the two charts
alt.hconcat(
    heatmap_select,
    field_select
    )

现在，我们对其进行翻译和本地化，使其更适合中文环境。

首先，我们需要导入必要的库：

import altair as alt
from vega_datasets import data

然后，我们加载数据集：

source = data.crime_heatmap.url

定义可能的分类变量所含的字符串如下：

fields = ['总计', '财产犯罪', '暴力犯罪', '车辆犯罪', '入室盗窃']

然后，我们定义热度图：

heatmap = alt.Chart(source).mark_rect().encode(
    alt.X('year(date):O', title=None),
    alt.Y('month(date):O', title=None),
    alt.Color('sum(crimes):Q', scale=alt.Scale(scheme='yellowgreenblue')),
).properties(
    width=600,
    height=300,
    title='月犯罪交叉热度图'
)

定义下拉选择框：

field_dropdown = alt.binding_select(options=fields)
field_select = alt.selection_single(fields='total', bind=field_dropdown, name='犯罪类型')